Bone screw and method for manufacturing the same

ABSTRACT

A bone screw and a method for manufacturing the same includes a screw thread configuration having one or more grooves cut into a leading face of the thread, a trailing face of the thread, and/or the shaft between the threads. Other implementations include the incorporation of facets into the one or more grooves. The implementation of the one or more grooves increases the surface are of the orthopedic screw and functions to increase in anchoring the bone screw within the bone once inserted therein, and thereby reduce the possibility for the screw backing out after insertion.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Divisional of co-pending U.S. patent applicationSer. No. 13/369,760 filed on Feb. 9, 2012, which was aContinuation-in-Part of U.S. Ser. No. 11/985,960 filed on Nov. 19, 2007,now U.S. Pat. No. 8,112,870 issued on Feb. 14, 2012.

BACKGROUND

1. Technical Field

The present principles relate to orthopedic (bone) screws. Moreparticularly, it relates to an orthopedic screw with increased surfacearea threading and the method for making the same.

2. Description of Related Art

Medical screws or Orthopedic (bone) screws or threaded pins are commonlyused in orthopedic procedures where it is required to set a bone ormultiple bones in a position that is secure with respect to either 1)the adjacent bone or bone part for which the screw is used; or 2) thesurgical splint or other external fixation device that is maintained inposition using the bone or orthopedic screw. As used herein, the term“bone screw” and/or “orthopedic screw” are interchangeably used hereinand shall include all known medical/orthopedic screws, threaded pinsand/or implants of any kind that are used in human and/or animal bones.

One common concern in the use of bone screws is the splitting of thebone during the insertion of the screw. Splitting often occurs when theworkpiece (e.g., bone) is brittle by nature, and the friction betweenthe screw and the bone requires higher torques to sufficiently penetratethe bone for proper application.

Another concern is the potential for the screws to loosen or “back out”after installation. This loosening can result in the mis-setting of abone and require supplemental procedures to be performed to correct thesame.

It is would therefore be desirable to have a bone screw that eliminatesthese problems without requiring any change in the current approvedprocedures for the installation and withdrawal of such bone screws.

SUMMARY

The faceted bone screw of the present principles will also reduce thelikelihood of bone screws and threaded pins backing out of the bone dueto improved osteointegration between the faceted threaded portion of theimplanted device and the bone.

According to one implementation, the method of manufacturing anorthopedic screw includes loading a bar stock of material into a screwcutting machine, moving a cutting tool into contact with the bar stockfor a predetermined amount of time to cut a portion of the thread,removing the cutting tool from cutting contact with the bar stock beforethe end of the predetermined amount of time, rotating either the barstock or cutting tool, moving the cutting tool back into contact withthe bar stock for a second predetermined amount of time to cut anotherportion of the thread, and removing the cutting tool from cuttingcontact with the bar stock before the end of the second predeterminedamount of time. The cutting of the bar stock is performed such that atleast two adjacent cuts have different radii with respect to a centralaxis of the bar stock.

Other aspects and features of the present principles will becomeapparent from the following detailed description considered inconjunction with the accompanying drawings. It is to be understood,however, that the drawings are designed solely for purposes ofillustration and not as a definition of the limits of the presentprinciples, for which reference should be made to the appended claims.It should be further understood that the drawings are not necessarilydrawn to scale and that, unless otherwise indicated, they are merelyintended to conceptually illustrate the structures and proceduresdescribed herein.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings wherein like reference numerals denote similarcomponents throughout the views:

FIG. 1 is cross sectional view of a bone screw according to the priorart;

FIGS. 2 a and 2 b are cross-sectional views of a faceted bone screwaccording to an implementation of the present principles;

FIG. 3 a is a plan view of the bone screw cutting machine that is usedto manufacture the bone screw according to an implementation of thepresent principles;

FIG. 3 b is a plan view of the bone screw cutting machine that is usedto manufacture the bone screw according to an implementation of thepresent principles;

FIG. 3 c is a plan view of the revolving guide bush of the screw cuttingmachine used to manufacture the bone screw of the present principles;

FIG. 4 is a flow diagram of the method for manufacturing a faceted bonescrew according to an implementation of the present principles;

FIG. 5 is a flow diagram of the method for manufacturing a faceted bonescrew according to an implementation of the present principles;

FIG. 6 is side view of a two threads of a screw for purposes ofdescribing the various portions thereof used herein;

FIG. 7; is a side view of a thread configuration for a bone/orthopedicscrew according to an implementation of the present principles;

FIG. 8 is a side view of two thread configurations for a bone/orthopedicscrew according to another implementation of the present principles;

FIGS. 9 a and 9 b are cross sectional views of the two threadconfigurations shown in FIG. 8;

FIG. 10 is a side view of a thread configuration for a bone/orthopedicscrew according to another implementation of the present principles;

FIG. 11 is a side view of a thread configuration for a bone/orthopedicscrew according to another implementation of the present principles;

FIG. 12 a is a side view of a thread configuration for a bone/orthopedicscrew according to another implementation of the present principles;

FIG. 12 b is a side view of a thread configuration for a bone/orthopedicscrew according to another implementation of the present principles;

FIG. 12 c is a side view of a thread configuration for a bone/orthopedicscrew according to another implementation of the present principles;

FIG. 13 is a side view of a thread configuration for a bone/orthopedicscrew according to another implementation of the present principles;

FIG. 14 is a side view of a thread configuration for a bone/orthopedicscrew according to another implementation of the present principles;

FIG. 15 is a side view of a thread configuration for a bone/orthopedicscrew according to another implementation of the present principles;

FIG. 16 is a side view of a thread configuration for a bone/orthopedicscrew according to another implementation of the present principles;

FIG. 17 is a side view of a thread configuration for a bone/orthopedicscrew according to another implementation of the present principles;

FIG. 18 is a side view of a thread configuration for a bone/orthopedicscrew according to another implementation of the present principles;

FIG. 19 is a side view of a thread configuration for a bone/orthopedicscrew according to another implementation of the present principles;

FIG. 20 is a side view of a thread configuration for a bone/orthopedicscrew according to another implementation of the present principles; and

FIGS. 21 a and 21 b show a side view of a thread configuration for abone/orthopedic screw according to another implementation of the presentprinciples.

DETAILED DESCRIPTION

FIG. 1 shows a cross section of a bone screw 10 according to the priorart. The shaft 12 includes a thread 14 that can extend any length of theshaft 12, including the entire length of the same. The thread generallyhas a consistent non-variable depth D depending on the particularapplication for that screw. The pitch, which relates to the distancebetween adjacent threads, is also generally consistent for most bonescrews and fasteners.

Those of ordinary skill in the art will recognize that one or moredifferent portions of the shaft 12 can include threads 14, oralternatively the entire shaft 12 can be threaded. These same conceptsapply to the bone screw of the present principles.

FIG. 2 a shows a cross section of a faceted bone screw 20 according toan implementation of the present principles. The bone screw 20 has ashaft 22 having threads 24 which include one or more facets 26 a, 26 band 26 c. These facets are generally transverse to the thread groove andextend across the same for some or part of the overall thread length.Although shown transverse to the thread, it is contemplated that thefacets may be offset from a pure transverse relationship with the threadgroove. By incorporating facets 26 into the shaft within the threadgroove 24, a plurality of peaks 28 and valleys 30 are formed therein.The facets 26 are disposed at different angles a and β with respect tothe next adjacent facet. The angles a can be in a range of 90-170degrees while the angles B can be in a range of 100-175 degrees. Theimplementation of the facets 26 will provide for a varying depth D ofthe thread.

As shown, there are several peaks 28 and valleys 30 formed by the facets26 at varying depths within the thread, each having rising/falling sidesdepending on the direction of rotation of the shaft 22. These peaks andvalleys, in conjunction with the rising/falling sides operate to reducethe friction between the bone and the screw and thereby operate toreduce the torque required to drive the bone screw into and remove froma bone. As will be appreciated, when the shaft 22 is rotated in onedirection, the rising sides of the respective peaks will graduallyoperate to penetrate the bone and once the peak is met, the frictionbetween the bone and the screw thread is substantially reduced as thebone passes over the falling side of that peak.

By repeating this process in a series like configuration throughout thethread, the overall torque required to drive the bone screw can bereduced by up to 50% (depending on the size of the screw and the bonebeing penetrated).

Once inserted into the bone, the bone will permit osteointegration withthe facets 26 (including the peaks and valleys), and the facets becomelike anchors for preventing the screw from loosening (i.e., “backingout”) after inserted by the doctor. However, when the bone screw must beextracted, a simple application of torque in the loosening directionwill cause the bone to loosen or break free from the facets 26, andfacets will once again operate to reduce the torque in required in theremoval of the bone screw.

FIG. 2 b shows another implementation of the bone screw 20 where thefacets 36 are concave in nature and the peaks are designated by thepoints 38 between the respective concave facets 36. In thisimplementation, the valleys would be considered at the base of eachconcave facet 36, and the friction reduction would be omni-directional(i.e., work the same in both clockwise and counterclockwise directions).As shown, there are differing radii R1, R2, R3, etc. that results fromthe formation of the concave facets 36 and the corresponding peaks andvalleys.

In order to manufacture the bone screw in a reproducible, certifiablemanner, a precise manufacturing technique is employed using a Swiss typescrew machine tool. Those of ordinary skill in the art will recognizethat this time tuning (i.e., lathe) or multiple axis Swiss type CNC(Computer Numerically Controlled) screw machine is only one example ofthe type of machine that could be properly configured to manufacture thefaceted bone screw disclosed herein, and that other types of machinesmay also be implemented without departing from the spirit of the presentprinciples.

FIG. 3 a shows a plan view of a Swiss cutting machine 300 used tomanufacture the bone screw of the present principles. This is thesliding headstock type CNC automatic lathe that is generally composed ofa headstock 302, a guide bushing (or guide collet) 304, a live toolholder 306, a sub spindle 308, and a tool holder slide 310. The toolholder slide includes one or more tools or dies 311 that can be usedduring other cutting processes. Although shown here for exemplarypurposes, the present principles may not require the tool holder slide310 during the process of manufacturing the faceted bone screw.

The headstock 302 includes a main spindle 312 and a sliding unit (notshown). The main spindle 312 chucks a bar with the guide bushing 304 andprovides it with rotary motion. The sliding unit provides reciprocatingaction on the material in the Z-axis direction (longitudinal) with theCNC control. Feeding of a bar in the ZI axis direction is provided bythe headstock during the main machining. The live tool holder 306includes a tool or cutter 307 that cuts the thread onto the (wires) barstock used to form the same.

FIG. 3 b shows a plan view of the live tool holder 306 of the Screwcutting lathe/machine 300. The live tool holder is capable ofreciprocating motion in the X-axis and Y-axis under the CNC Control, andwill feed material in a diametric direction during main machining. Thetool post makes the cutting tool contact the bar near the guide bushing304 and cooperates with the headstock 302 to execute the machining. Thetool holder (not shown), the 4-spindle sleeve holder 314 and the4-spindle cross drilling/milling unit 316 are attached to the tool post.The cutting tool will be attached to the tool holder to execute turning.

The front machining tool holder is attached to the sleeve holder 314,and executes a front drilling, tapping and boring action. Power driventools can be attached to the 4-spindle cross unit 316, providing arotating motion for drilling, tapping and end milling, etc., to performcross or front drilling, tapping and milling.

The X-axis performs a diameter direction feed of the tool holder and thetool selection of the 4-spindle cross drilling/milling unit. The Y-axisperforms the tool selection of the tool holder, tool selection of thesleeve holder 314 and a diameter direction feed of the 4-spindle crossdrilling/milling unit 316.

The guide bushing 304 supports a bar near the machining position toprevent material from bending, and thereby helps to achieve highlyaccurate and reproducible machining. In this unit, the guide bushing 304supports most of the cutting load in the diametric direction, and themachining accuracy is somewhat dependent on the clearance between theguide bushing 304 and the bar. Therefore, selection of the bar is basedon the precision required for the outer diameter of the material beingcut with the threads of the present principles. The guide bushing 304 ispreferably a revolving guide bush 320 (see FIG. 3 c) that issynchronized with the main spindle. Generally the guide bush 320 ispositioned within the guide bushing 304.

The sub spindle 313 chucks a bar with the guide bushing (collet) 304 andprovides a rotary motion. The sliding unit provides materialreciprocation in the ZB-axis direction (longitudinal) and the XB-axisdirection with the CNC control.

The tool holder 310 provides ZB-axis direction feed in the backmachining, and XB-axis direction feed in the tool selection ofsub-spindle unit 308. The various roles of the back attachment machiningcan be roughly classified as follows:

Non-pip machining: The back attachment chucks a work piece in thecutting process and performs the cutting process by synchronous rotationwith the main spindle so as to obtain a cutting-off surface withoutdowel.

Z-ZB synchronous control: The back attachment chucks a work piece at thesame time with the main spindle during the main machining. It alsoperforms a synchronous operation in direction of the Z/ZB-axis, or makesa synchronous rotation with a main spindle so that it suppresses bendingor warping of the bar.

Back machining: The live tool holder 306 performs back machining of thecutting-end surface and periphery thereof in cooperation with the backsub-spindle unit 308 of the tool post.

Sub-spindle unit 308 <This is not included in type 540S of the machine>:The tool holder 306 for machining of the cutting-end surface is attachedto the back machining sub-spindle unit 308 to perform the backsidedrilling, tapping and boring. Selecting the drive system for powerdriven attachment (this is an option) permits the attachment of apower-driven tool until and the machining of the back off-centertapping/milling.

FIG. 4 shows the method 400 for manufacturing the faceted bone screw inaccordance with a semi-automatic implementation. In accordance with onemethod of the present principles, a bar stock of desired material isloaded (402) into the bar feeder. A collet is installed (404) in thework holding axis. A custom made guide bushing, fabricated to the sizerequire to produce a desired level of clearance related harmonics, isinstalled (406) into the machine spindle axis. A circular threading toolwhich has been ground to produce the desired thread configuration isinstalled (408) one a live tool holder.

According to one aspect, the facets of the faceted bone screw areapplied through a precisely controlled vibratory effect through theapplication of clearance related harmonics during the screw cuttingprocess. Thus, by adjusting the size of the guide bushing (guide collet)we can define the clearing between the same and the bar stock. This“clearance” generates a clearance related harmonic (or a controlledvibratory effect) as the bar stock is fed through the spindle axispassing by the rotating circular threading tool which is generating thethread configuration onto the bar stock. Through the control of theclearance, the vibratory effect is accurately controlled. Examples ofsuch clearance would be 0.0002-0.005 inches.

Those of skill in the art will recognize that the Swiss type screwmachine is a computer programmable machine, and as such, theaforementioned processed can be computer controlled by the machine onceprogrammed accordingly. For example, the machine can be programmed sothe threading tool produces the thread configuration in one pass ormultiple passes, depending on the size of the bar stock, the amount ofmaterial to be machined, and desired finish.

Other multiple features of the faceted bone screw can be performed priorto, or after, the thread configuration is generated onto the bar stock,such as screw head generation, drilling pilot details, driveconfigurations, coatings and/or any further surface preparationtreatments, etc.

FIG. 5 shows another method for manufacturing the bone screw accordingto the present principles. As mentioned above, in order to manufacturethe bone screw in a reproducible, certifiable manner, a precisemanufacturing technique is employed using a Swiss type screw machinetool. Although the Swiss type scree machine tool described above is onepreferred machine for manufacturing the bone screw of the presentprinciples, other machinery that enables the selective rotation of thebar stock and selective cutting of the same may also be employed withoutdeparting from the scope of the invention. According to this method 500,the bar stock is loaded (502) into a thread cutting machine. Thisloading can be done before or after a head is formed on the bar stock.Once loaded, in one implementation, the bar stock is incrementallyrotated with distinct pauses between each incremental rotation (504). Inanother implementation, the bar stock is stationary and the cutting toolis incrementally rotated around the bar stock. The time duration foreach pause between incremental rotations of either the bar stock or thecutting tool can be varied depending on the desired thread design andconfiguration. Such time duration can be anywhere from 0.1-5 seconds.During each pause, the thread cutting tool is moved into contact withthe bar stock to cut the thread for the same (506). The movement of thecutting tool into contact with the bar stock can be performed radiallywith respect to the bar stock, or could be angularly offset from aradial approach so as to enable variations in the thread designs to bedescribed below with respect to FIGS. 6-20. In this manner, the depth(or radial penetration) of the cutting tool into the bar stock can beinfinitely varied (without compromising the integrity of the bar stockused to create the screw), thus creating different radii (i.e., measuredfrom the center of the screw shaft—see for example FIG. 2 b) throughoutthe cutting of the thread resulting in the faceted screw configuration.Once the cutting is completed for that pause period, the cutting tool ismoved away from the bar stock (508), and the cycle is repeated (510)until the desired portion of the thread has been cut into the bar stock.

In accordance with the above noted implementation where the bar stock isheld stationary, a rotating cutting head/tool is controlled to impartthe thread cutting that is performed with predetermined time periodsbetween cutting actions. Here, the rotating cutting tool may be rotatedanywhere from 0.01-90 degrees before imparting the cutting to thestationary bar stock. The radial penetration of the rotating cuttingtool into the bar stock can also be varied in order to impart thefaceted configuration to the bar stock. Each cutting action will beperformed for a predetermined amount of time before moving the cuttinghead out of contact with the bar stock. For example, after a firstcutting action, the rotating cutting tool is moved out of contact withthe stationary bar stock, rotated a predetermined amount, and thenbrought back into contact with the stationary bar stock for anotherpredetermined amount of time to implement the second cutting action onthe next portion of the thread. Those of skill in the art willappreciate that two adjacent cuts of however slight differing radii willresult in the formation of adjacent concave thread cuts, thereby formingthe concave facets in the same.

FIG. 6 shows a side view of a portion of a threaded fastener 600 forshowing the various parts of the same. Those of skill in the art willclearly recognize that any threaded fastener has a thread pitch P whichis the distance between adjacent threads 604. A shaft 602 is essentiallythe remaining portion of the bar stock between the threads 604 formedtherein. Each thread 604 includes a leading face/surface 606 and atrailing face/surface 608, usually connected at the peak or crest 610.As will be described below with reference to the remaining embodiments,any one or more combinations of the following embodiments may be made toa single bone/orthopedic screw without departing from the scope ofpresent principles as disclosed herein.

FIG. 7 shows an implementation of a bone/orthopedic screw 700 where oneor more grooves 702 are cut into the trailing face of the thread. Withineach groove 702 is an additional thread 704 of any preferredconfiguration. In the example shown, the additional thread 704 has anupside down V cross section. By cutting the grooves 702 into thetrailing face of the thread, the surface area of the same is increased.By adding the internal thread 704, there is now additional surface areato which the bone may adhere, and increase further osteointegration withthe same. According to an exemplary implementation, the grooves 702 arespaced from each other but sufficiently close enough to each other tocreate a pitch between the side faces of two adjacent grooves. In otherwords, the material between adjacent grooves 702 forms a crest, whichadds a smaller recessed thread within the trailing face of the largerthreads.

FIG. 8 shows alternative implementations for the added groove 702. Onthe left example, the groove 702 is circumferentially cut into thetrailing face of the thread, and can include one or more facets 804 cutinto the same. On the right example, the grooves 802 are cut radiallyinto the trailing face and leading face of the screw threads and mayalso include one or more facets 804 cut into the same. FIGS. 9 a and 9 bshow cross sectional views of the left and right examples of FIG. 8showing the circumferential groove 704. In this implementation, theaddition of the grooves 702 or 802 increases the surface area of thelarger thread and maximizes the area available for introduction offacets in an otherwise non-faceted screw.

FIG. 10 shows a modified implementation of the embodiment shown in FIG.7 where the additional thread 704 includes one or more facets 1000 onthe surfaces thereof. Again, the addition of groove 702 with the thread704 contained therein increases the available surface area of thetrailing face of the thread. The further addition of facets 1000 furtherincreases the already increased surface area of the thread 704.

FIG. 11 shows a further modified implementation of the embodiment shownin FIG. 10. In this implementation, the remaining space between thegrooves 702 on the trailing face of the thread includes more or morefacets 1010.

FIG. 12 a shows an implementation of the bone/orthopedic screw 1200according to the present principles. Here, a spiral groove 1202 is addedto the shaft between adjacent threads. The spiral groove 1202 increasesthe surface area of the shaft portion between the threads. In thisexample, the size of space 1203 between the grooves 1202 can be changedaccording to any preferred design configuration. For example, it isherein contemplated that the spacing 1203 can be in a range of 0.001-0.5inches depending on the spacing of the respective threads 604. FIGS. 12b and 12 c show this concept where the spacing 1203 has been reducedsuch that groove 1202 essentially forms another thread within the shaftof the screw. Here, each space 1203 functions as the crest or peak ofthe new thread created by the groove 1202. In the example of FIG. 12 c,facets are added to the groove 1202, and could also be added to thesurface of the crest formed by the space 1203 between the grooves 1202.Here, the added groove does not extend beyond the shape of the originalscrew/shaft, and is an addition to the same (i.e. is recessed into theexisting shaft of the threaded screw).

FIG. 13 shows another implementation where one or more facets 1204 areadded to the groove 1202. FIG. 14 shows the groove 1202 with the addedthread 1208 disposed therein. The additional thread 1208 (or upside downV cross section) operates to further increase the exposed surface areaof the groove 1202. FIG. 15 shows the thread 1208 having one or morefacets 1210 on one or both of the respective faces thereof. FIG. 16shows a further modification where the spacing 1203 includes one or morefacets 1600. In another exemplary implementation (as shown in FIGS. 12 band 12 c), the space 1203 is very small between adjacent spiral grooves1202, such that the space 1203 itself forms a crest between the adjacentspiral groove 1202. This crest will further function as a slightlylarger diameter thread between the grooves formed in the shaft.

FIGS. 17 and 18 show another implementation of the bone/orthopedic screw1700 according to the present principles. Here the groove 1710 is Vshaped in cross section. One or more facets 1712 can be added to eitheror both surfaces of the V-shaped groove (FIG. 18). As with theembodiment shown in FIGS. 12 b and 12 c, the spacing between adjacentgrooves 1710 can be such that the crest between adjacent grooves couldfunction as a crest or peak of an internal thread formed by the groove1710. FIGS. 19 and 20 show yet another implementation of thebone/orthopedic screw 1900, according to the present principles. Here,facets 1902 can be added to the trailing face of the thread, and/orfacets 1904 can be added to the leading face of the thread. In theimplementations shown, these facets are radially disposed on thetrailing face or leading face of the thread, however as described abovewith respect to the several other contemplated implementations; thefacet configurations can be circumferential, longitudinal and/or radialwithout departing from the intended scope of the invention. In additionto the facets 1902 and 1904, the shaft of the screw between the threadscan also include facets 1906.

FIG. 21 a shows an alternative configuration of the bone screw threadwhere the peak or crest 2110 of the thread is enlarged between thetrailing face 2108 and the leading face 2106. FIG. 21 b shows a furtherimplementation where a groove 2112 is cut into the enlarged peak/crest2110. This will operate to increase the surface area of the peak/crest2110 and significantly increase the osteointegration capability of thesame.

Those of skill in the art will appreciate that the above variations ofthe bone screw and the use of additional grooves and/or different facetconfigurations may be mixed and matched according to a desired orspecific application to which the bone screw will be used. Suchapplications can include, but are clearly not limited to corticalscrews, cancellous screws, headless compression screws, externalfixation screws and/or pins, guide wires, implants, implant anchors,etc.

In accordance with other contemplated implementations, thebone/orthopedic screw and/or the grooves cut therein of the presentprinciples may be further coated, treated and/or applied with withvarious types of coatings/treatments which provide further enhancementto the respective applications of the bone screw. Here, these coatingscould be applied to any part or portion of the bone screw.

For example, the bone screw of the present principles may bemanufactured and then coated with medications or other treatments thatpromote osteointegration, prevent infection and/or deliver one or moremedications in one or more varying volumes to the areas around the bonescrew (i.e., either the areas of bone around the screw that is insertedinto the bone and/or the areas of bone screw that are not within thebone but are still within the patient's body). Some examples of suchcoatings and method for applying them can be found in U.S. Pat. Nos.7,875,285, 7,879,086, 8,028,646, 7,913,642 and 7,901,453, each of whichis incorporated herein by reference. Those of skill in the art willappreciate that any coating or treatment could be added to thebone/orthopedic screw of the present principles without departing fromthe scope of the same. This may include films or coatings that dissolveonce within the human body. Other possible coatings or files may alsoinclude those that facilitate bone growth (e.g., bone growth hormones).

Those of skill in the art will recognize that the “bar stock” referredto throughout this specification is the material which theorthopedic/bone screw is made of Examples of this material, as they arecurrently being used are Titanium, Stainless Steel, cobalt chromium, andabsorbable biocompatible plastics. The present principles may also beapplied to any known or not yet known material used for orthopedic/boneapplications. It is further contemplated herein that the head of thebone screws and or the tips can be made in any preferred form for aparticular bone application/penetration without departing from theintended scope of the present principles. It is also contemplated thatthe bar stock on which the threads of the present principles are appliedmay also be hollow and may include internal threads for connection ofother fixation devices, or orthopedic alignment devices, etc.

It is to be understood that the present principles may be implemented invarious forms of hardware, software, firmware, special purposeprocessors, or a combination thereof. Preferably, the present principlesmay be implemented as a combination of hardware and software. Moreover,the software is preferably implemented as an application programtangibly embodied on a program storage device. The application programmay be uploaded to, and executed by, a machine comprising any suitablearchitecture. Preferably, the machine is implemented on a computerplatform having hardware such as one or more central processing units(CPU), a random access memory (RAM), and input/output interface(s). Thecomputer platform also includes an operating system and microinstructioncode. The various processes and functions described herein may either bepart of the microinstruction code or part of the application program (ora combination thereof) that is executed via the operating system. Inaddition, various other peripheral devices may be connected to thecomputer platform such as an additional data storage device and aprinting device.

It is to be further understood that, because some of the constituentsystem components and method steps depicted in the accompanying Figuresare preferably implemented in software, the actual connections betweenthe system components (or the process steps) may differ depending uponthe manner in which the present principles is programmed. Given theteachings herein, one of ordinary skill in the related art will be ableto contemplate these and similar implementations or configurations ofthe present principles.

While there have been shown, described and pointed out fundamental novelfeatures of the present principles, it will be understood that variousomissions, substitutions and changes in the form and details of themethods described and devices illustrated, and in their operation, maybe made by those skilled in the art without departing from the spirit ofthe same. For example, it is expressly intended that all combinations ofthose elements and/or method steps which perform substantially the samefunction in substantially the same way to achieve the same results arewithin the scope of the present principles. Moreover, it should berecognized that structures and/or elements and/or method steps shownand/or described in connection with any disclosed form or implementationof the present principles may be incorporated in any other disclosed,described or suggested form or implementation as a general matter ofdesign choice. It is the intention, therefore, to be limited only asindicated by the scope of the claims appended hereto.

What is claimed is:
 1. An orthopedic screw comprising: a shaft; a threadcut into at least a portion of said shaft, said threads having a leadingedge, a trailing edge and a depth; at least one groove formed in one ofthe leading edge or the trailing edge and configured to increase asurface area of the respective leading or trailing edge; and at leastone facet cut into the at least one groove.
 2. The orthopedic screw ofclaim 1, wherein the at least one groove is radially cut into theleading or trailing edge of the thread.
 3. The orthopedic screw of claim2, wherein the at least one groove is cut into the leading or trailingedge of the thread with a varying radii with respect to the shaftthroughout the groove.
 4. The orthopedic screw of claim 1, wherein saidat least one groove has a V-shaped cross section.
 5. The orthopedicscrew of claim 1, wherein the at least one groove has an upside downV-shaped cross section.
 6. The orthopedic screw of claim 1, furthercomprising at least one groove formed in the other of the leading edgeor trailing edges of the thread.
 7. An orthopedic screw comprising: ashaft; a plurality of first threads cut into at least a portion of saidshaft, said first threads having a leading edge, a trailing edge and adepth; at least one spiral groove formed in one of the leading edge orthe trailing edge of the first thread and being configured to increase asurface area of the respective leading or trailing edge; and at leastone facet cut into the at least one spiral groove.
 8. The orthopedicscrew of claim 7, wherein said spiral groove is formed such that itdefines a second thread within the leading or trailing edge of the firstthread.
 9. The orthopedic screw of claim 7, wherein said at least onespiral groove has a V-shaped cross section.
 10. The orthopedic screw ofclaim 7, wherein the at least one spiral groove has an upside downV-shaped cross section.